1. Field of the Invention
The present invention relates to a power load control system capable of absorbing a variation of total power consumption of power equipments, such as heat pump water heaters, which matches to a high frequency component of the fluctuation of a total generated power caused by a variety of power generators, such as a wind power generator and a solar power generator which are known to have a high frequency component in its fluctuation of the generated power (here, the power being the averaged power which is averaged over once cycle). The present invention provides efficient ways to use a total generated power when it has relatively high frequency components in its generated power, and provides a safe-guard for a power supplying system to avoid undesirable deviation of the system frequency, for example.
2. Description of the Related Art
The electrical power supplier has major ways to generate electric powers, such as a nuclear power generation, a thermal power generation, and a hydraulic power generation. Here the frequency of the output power from the thermal power plant and the hydraulic power plant are controlled by using the feedback of the variation of the power consumption through the central power feeding controller. The system frequency is currently controlled by the following three ways: 1) Economic load Dispatching Control (EDC) which is a way of scheduling to generate the power which meets the power demand with the least cost in generating power by using connected power generators. EDC has the typical response time of 20 minutes or longer. 2) Load Frequency Control (LFC) which is a scheme to balance the generated power with the power demand by adjusting power outputs of power generators. LFC has the typical response time of several minutes or longer. 3) Governor Control which is done by adjusting the power of the generators by controlling the boiler pressure and the turbine speed of the thermal power generators. The Governor Control has the typical response time of 20 seconds or longer.
The electric powers generated by wind power generators and the solar power generators are examples of so-called clean energies. The wind power generators and the solar power generators can contribute to reducing the emission of the exhaust gases, the green house gases, which cause environmental problems. The electric powers generated by the wind power generators or the solar power generators are known to fluctuate in a short time range according to the weather conditions, and therefore have high frequency components in the fluctuation of the generated power which sometimes varies within a time range of less than about 10 seconds. None of the above mentioned ways to control the supplying system frequency, Economic load Dispatching Control (EDC), Load Frequency Control (LFC), and Governor Control, is able to respond properly to control the fluctuation of the total generated power within a short time range of less than about 10 seconds. Storing the high frequency component of the generated power by generators including the wind power generators and the solar power generators in batteries with a large capacity is one way to regulate the system frequency. But installing large capacity batteries in the power system is not a cost effective method with currently existing technologies. When a total generated power exceeds a total consumption of power in an instance, an excess of generated power is lost by a heat loss for example, and when a total generated power is short of a total consumption of power in an instance, a supply voltage may drop out of a predetermined voltage range. In both case, it happens that a total generated power is not consumed efficiently by power equipments.